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<div class="titlepage"><div><div><h6 class="title">
<a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1"></a><a class="link" href="overload1.html" title="websocket::stream::async_handshake (1 of 2 overloads)">websocket::stream::async_handshake
          (1 of 2 overloads)</a>
</h6></div></div></div>
<p>
            Perform the WebSocket handshake asynchronously in the client role.
          </p>
<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h0"></a>
            <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.synopsis"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.synopsis">Synopsis</a>
          </h7><pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">class</span> <span class="identifier">HandshakeHandler</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special">&lt;</span><a class="link" href="../executor_type.html" title="websocket::stream::executor_type">executor_type</a><span class="special">&gt;&gt;</span>
<a href="../../../../../../../../doc/html/boost_asio/reference/asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type" target="_top"><span class="emphasis"><em>DEDUCED</em></span></a>
<span class="identifier">async_handshake</span><span class="special">(</span>
    <span class="identifier">string_view</span> <span class="identifier">host</span><span class="special">,</span>
    <span class="identifier">string_view</span> <span class="identifier">target</span><span class="special">,</span>
    <span class="identifier">HandshakeHandler</span><span class="special">&amp;&amp;</span> <span class="identifier">handler</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special">&lt;</span> <a class="link" href="../executor_type.html" title="websocket::stream::executor_type">executor_type</a> <span class="special">&gt;{});</span>
</pre>
<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h1"></a>
            <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.description"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.description">Description</a>
          </h7><p>
            This initiating function is used to asynchronously begin performing the
            <a href="https://en.wikipedia.org/wiki/WebSocket#Protocol_handshake" target="_top">WebSocket
            handshake</a>, required before messages can be sent and received.
            During the handshake, the client sends the Websocket Upgrade HTTP request,
            and the server replies with an HTTP response indicating the result of
            the handshake. This call always returns immediately. The asynchronous
            operation will continue until one of the following conditions is true:
          </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
                The request is sent and the response is received.
              </li>
<li class="listitem">
                An error occurs.
              </li>
</ul></div>
<p>
            The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>,
            is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code>
            and <code class="computeroutput"><span class="identifier">async_write_some</span></code>
            functions. No other operation may be performed on the stream until this
            operation completes. The handshake is successful if the received HTTP
            response indicates the upgrade was accepted by the server, represented
            by a <a href="https://tools.ietf.org/html/rfc7230#section-3.1.2" target="_top">status-code</a>
            of <a class="link" href="../../boost__beast__http__status.html" title="http::status"><code class="computeroutput"><span class="identifier">beast</span><span class="special">::</span><span class="identifier">http</span><span class="special">::</span><span class="identifier">status</span><span class="special">::</span><span class="identifier">switching_protocols</span></code></a>.
          </p>
<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h2"></a>
            <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.parameters"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.parameters">Parameters</a>
          </h7><div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                    <p>
                      Name
                    </p>
                  </th>
<th>
                    <p>
                      Description
                    </p>
                  </th>
</tr></thead>
<tbody>
<tr>
<td>
                    <p>
                      <code class="computeroutput"><span class="identifier">host</span></code>
                    </p>
                  </td>
<td>
                    <p>
                      The name of the remote host. This is required by the HTTP protocol
                      to set the "Host" header field. The implementation
                      will not access the string data after the initiating function
                      returns.
                    </p>
                  </td>
</tr>
<tr>
<td>
                    <p>
                      <code class="computeroutput"><span class="identifier">target</span></code>
                    </p>
                  </td>
<td>
                    <p>
                      The request-target, in origin-form. The server may use the
                      target to distinguish different services on the same listening
                      port. The implementation will not access the string data after
                      the initiating function returns.
                    </p>
                  </td>
</tr>
<tr>
<td>
                    <p>
                      <code class="computeroutput"><span class="identifier">handler</span></code>
                    </p>
                  </td>
<td>
                    <p>
                      The completion handler to invoke when the operation completes.
                      The implementation takes ownership of the handler by performing
                      a decay-copy. The equivalent function signature of the handler
                      must be:
                    </p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
    <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">ec</span>    <span class="comment">// Result of operation</span>
<span class="special">);</span>
</pre>
                    <p>
                      Regardless of whether the asynchronous operation completes
                      immediately or not, the handler will not be invoked from within
                      this function. Invocation of the handler will be performed
                      in a manner equivalent to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>.
                    </p>
                  </td>
</tr>
</tbody>
</table></div>
<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h3"></a>
            <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.example"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.example">Example</a>
          </h7><pre class="programlisting"><span class="identifier">ws</span><span class="special">.</span><span class="identifier">async_handshake</span><span class="special">(</span><span class="string">"localhost"</span><span class="special">,</span> <span class="string">"/"</span><span class="special">,</span>
    <span class="special">[](</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">)</span>
    <span class="special">{</span>
        <span class="keyword">if</span><span class="special">(</span><span class="identifier">ec</span><span class="special">)</span>
            <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special">&lt;&lt;</span> <span class="string">"Error: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">ec</span><span class="special">.</span><span class="identifier">message</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="string">"\n"</span><span class="special">;</span>
    <span class="special">});</span>
</pre>
<h7><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.h4"></a>
            <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_handshake.overload1.see_also"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_handshake.overload1.see_also">See
            Also</a>
          </h7><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
                <a href="https://tools.ietf.org/html/rfc6455#section-4.1" target="_top">Websocket
                Opening Handshake Client Requirements (RFC6455)</a>
              </li>
<li class="listitem">
                <a href="https://tools.ietf.org/html/rfc7230#section-5.4" target="_top">Host
                field (RFC7230)</a>
              </li>
<li class="listitem">
                <a href="https://tools.ietf.org/html/rfc7230#section-3.1.1" target="_top">request-target
                (RFC7230)</a>
              </li>
<li class="listitem">
                <a href="https://tools.ietf.org/html/rfc7230#section-5.3.1" target="_top">origin-form
                (RFC7230)</a>
              </li>
</ul></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie
      Falco<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
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